Three phase basic question

[Traineesparks]

Hi, i am just doing some revision on three phase and ive come across a question which i would just like some clarification on the correct answer please

Question -

A balance star - connected three phase load of 10ohms per phase is supplied from a 400V 50 Hz mains supply at unity power,

Calculate the a) phase voltage

B) line current

c) the total power consumed

Ok so im happy with my 1st answer as 230.94V Because VL = 1.732 X VP so 400V / 1.732 = 230.94V

But on question b to work out the line current do i divide 230V (Phase Voltage) by 10 ohms or 400V (Line Voltage) by 10 ohms

I am sure it is the Phase Voltage 230V but just want a few yes' lol

thanks

 

[ProDave]

As it's STAR connected, each winding of the motor sees the phase to neutral voltage, so you would calculate the current based on the phase voltage of 230.94V

The star point is in effect neutral, though in the case of a motor it's not usually connected anywhere.

If the motor had been Delta connected, then each winding would see the phase to phase voltage of 400V so your calculations would be done on that.

 

[Traineesparks]

As it's STAR connected, each winding of the motor sees the phase to neutral voltage, so you would calculate the current based on the phase voltage of 230.94VThe star point is in effect neutral, though in the case of a motor it's not usually connected anywhere.

If the motor had been Delta connected, then each winding would see the phase to phase voltage of 400V so your calculations would be done on that.

Thanks, thought i was right but just wanted to bee 100%